In recent years, using communication networks such as the Internet desired content has been enjoyed from an enormous amount of content. Since available content amounts to an enormous quantity, various types of recommendation techniques have also been proposed. For example, there is a technique for retrieving user's favorite types of content, and presenting the content to a user (see, for example, JP-A-2006-58947). On the other hand, a technique of content-based filtering has also been proposed for detecting content having feature information with a high similarity to feature information of a user's favorite content.